/*
 * Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under both the BSD-style license (found in the
 * LICENSE file in the root directory of this source tree) and the GPLv2 (found
 * in the COPYING file in the root directory of this source tree).
 * You may select, at your option, one of the above-listed licenses.
 */

/* This header contains definitions
 * that shall **only** be used by modules within lib/compress.
 */

#ifndef ZSTD_COMPRESS_H
#define ZSTD_COMPRESS_H

/*-*************************************
 *  Dependencies
 ***************************************/
#include "zstd_internal.h"
#ifdef ZSTD_MULTITHREAD
#include "zstdmt_compress.h"
#endif

#if defined(__cplusplus)
extern "C" {
#endif

/*-*************************************
 *  Constants
 ***************************************/
#define kSearchStrength 8
#define HASH_READ_SIZE 8
#define ZSTD_DUBT_UNSORTED_MARK                                                                                       \
  1 /* For btlazy2 strategy, index 1 now means "unsorted".                                                            \
       It could be confused for a real successor at index "1", if sorted as larger than its predecessor.              \
       It's not a big deal though : candidate will just be sorted again.                                              \
       Additionnally, candidate position 1 will be lost.                                                              \
       But candidate 1 cannot hide a large tree of candidates, so it's a minimal loss.                                \
       The benefit is that ZSTD_DUBT_UNSORTED_MARK cannot be misdhandled after table re-use with a different strategy \
       Constant required by ZSTD_compressBlock_btlazy2() and ZSTD_reduceTable_internal() */

/*-*************************************
 *  Context memory management
 ***************************************/
typedef enum { ZSTDcs_created = 0, ZSTDcs_init, ZSTDcs_ongoing, ZSTDcs_ending } ZSTD_compressionStage_e;
typedef enum { zcss_init = 0, zcss_load, zcss_flush } ZSTD_cStreamStage;

typedef struct ZSTD_prefixDict_s {
  const void* dict;
  size_t dictSize;
  ZSTD_dictContentType_e dictContentType;
} ZSTD_prefixDict;

typedef struct {
  U32 CTable[HUF_CTABLE_SIZE_U32(255)];
  HUF_repeat repeatMode;
} ZSTD_hufCTables_t;

typedef struct {
  FSE_CTable offcodeCTable[FSE_CTABLE_SIZE_U32(OffFSELog, MaxOff)];
  FSE_CTable matchlengthCTable[FSE_CTABLE_SIZE_U32(MLFSELog, MaxML)];
  FSE_CTable litlengthCTable[FSE_CTABLE_SIZE_U32(LLFSELog, MaxLL)];
  FSE_repeat offcode_repeatMode;
  FSE_repeat matchlength_repeatMode;
  FSE_repeat litlength_repeatMode;
} ZSTD_fseCTables_t;

typedef struct {
  ZSTD_hufCTables_t huf;
  ZSTD_fseCTables_t fse;
} ZSTD_entropyCTables_t;

typedef struct {
  U32 off;
  U32 len;
} ZSTD_match_t;

typedef struct {
  int price;
  U32 off;
  U32 mlen;
  U32 litlen;
  U32 rep[ZSTD_REP_NUM];
} ZSTD_optimal_t;

typedef enum { zop_dynamic = 0, zop_predef } ZSTD_OptPrice_e;

typedef struct {
  /* All tables are allocated inside cctx->workspace by ZSTD_resetCCtx_internal() */
  unsigned* litFreq;          /* table of literals statistics, of size 256 */
  unsigned* litLengthFreq;    /* table of litLength statistics, of size (MaxLL+1) */
  unsigned* matchLengthFreq;  /* table of matchLength statistics, of size (MaxML+1) */
  unsigned* offCodeFreq;      /* table of offCode statistics, of size (MaxOff+1) */
  ZSTD_match_t* matchTable;   /* list of found matches, of size ZSTD_OPT_NUM+1 */
  ZSTD_optimal_t* priceTable; /* All positions tracked by optimal parser, of size ZSTD_OPT_NUM+1 */

  U32 litSum;                  /* nb of literals */
  U32 litLengthSum;            /* nb of litLength codes */
  U32 matchLengthSum;          /* nb of matchLength codes */
  U32 offCodeSum;              /* nb of offset codes */
  U32 litSumBasePrice;         /* to compare to log2(litfreq) */
  U32 litLengthSumBasePrice;   /* to compare to log2(llfreq)  */
  U32 matchLengthSumBasePrice; /* to compare to log2(mlfreq)  */
  U32 offCodeSumBasePrice;     /* to compare to log2(offreq)  */
  ZSTD_OptPrice_e priceType;   /* prices can be determined dynamically, or follow a pre-defined cost structure */
  const ZSTD_entropyCTables_t* symbolCosts; /* pre-calculated dictionary statistics */
} optState_t;

typedef struct {
  ZSTD_entropyCTables_t entropy;
  U32 rep[ZSTD_REP_NUM];
} ZSTD_compressedBlockState_t;

typedef struct {
  BYTE const* nextSrc;  /* next block here to continue on current prefix */
  BYTE const* base;     /* All regular indexes relative to this position */
  BYTE const* dictBase; /* extDict indexes relative to this position */
  U32 dictLimit;        /* below that point, need extDict */
  U32 lowLimit;         /* below that point, no more data */
} ZSTD_window_t;

typedef struct ZSTD_matchState_t ZSTD_matchState_t;
struct ZSTD_matchState_t {
  ZSTD_window_t window; /* State for window round buffer management */
  U32 loadedDictEnd;    /* index of end of dictionary */
  U32 nextToUpdate;     /* index from which to continue table update */
  U32 nextToUpdate3;    /* index from which to continue table update */
  U32 hashLog3;         /* dispatch table : larger == faster, more memory */
  U32* hashTable;
  U32* hashTable3;
  U32* chainTable;
  optState_t opt; /* optimal parser state */
  const ZSTD_matchState_t* dictMatchState;
  ZSTD_compressionParameters cParams;
};

typedef struct {
  ZSTD_compressedBlockState_t* prevCBlock;
  ZSTD_compressedBlockState_t* nextCBlock;
  ZSTD_matchState_t matchState;
} ZSTD_blockState_t;

typedef struct {
  U32 offset;
  U32 checksum;
} ldmEntry_t;

typedef struct {
  ZSTD_window_t window; /* State for the window round buffer management */
  ldmEntry_t* hashTable;
  BYTE* bucketOffsets; /* Next position in bucket to insert entry */
  U64 hashPower;       /* Used to compute the rolling hash.
                        * Depends on ldmParams.minMatchLength */
} ldmState_t;

typedef struct {
  U32 enableLdm;      /* 1 if enable long distance matching */
  U32 hashLog;        /* Log size of hashTable */
  U32 bucketSizeLog;  /* Log bucket size for collision resolution, at most 8 */
  U32 minMatchLength; /* Minimum match length */
  U32 hashRateLog;    /* Log number of entries to skip */
  U32 windowLog;      /* Window log for the LDM */
} ldmParams_t;

typedef struct {
  U32 offset;
  U32 litLength;
  U32 matchLength;
} rawSeq;

typedef struct {
  rawSeq* seq;     /* The start of the sequences */
  size_t pos;      /* The position where reading stopped. <= size. */
  size_t size;     /* The number of sequences. <= capacity. */
  size_t capacity; /* The capacity starting from `seq` pointer */
} rawSeqStore_t;

struct ZSTD_CCtx_params_s {
  ZSTD_format_e format;
  ZSTD_compressionParameters cParams;
  ZSTD_frameParameters fParams;

  int compressionLevel;
  int forceWindow; /* force back-references to respect limit of
                    * 1<<wLog, even for dictionary */

  ZSTD_dictAttachPref_e attachDictPref;

  /* Multithreading: used to pass parameters to mtctx */
  int nbWorkers;
  size_t jobSize;
  int overlapLog;
  int rsyncable;

  /* Long distance matching parameters */
  ldmParams_t ldmParams;

  /* Internal use, for createCCtxParams() and freeCCtxParams() only */
  ZSTD_customMem customMem;
}; /* typedef'd to ZSTD_CCtx_params within "zstd.h" */

struct ZSTD_CCtx_s {
  ZSTD_compressionStage_e stage;
  int cParamsChanged; /* == 1 if cParams(except wlog) or compression level are changed in requestedParams. Triggers
                         transmission of new params to ZSTDMT (if available) then reset to 0. */
  int bmi2; /* == 1 if the CPU supports BMI2 and 0 otherwise. CPU support is determined dynamically once per context
               lifetime. */
  ZSTD_CCtx_params requestedParams;
  ZSTD_CCtx_params appliedParams;
  U32 dictID;

  int workSpaceOversizedDuration;
  void* workSpace;
  size_t workSpaceSize;
  size_t blockSize;
  unsigned long long pledgedSrcSizePlusOne; /* this way, 0 (default) == unknown */
  unsigned long long consumedSrcSize;
  unsigned long long producedCSize;
  XXH64_state_t xxhState;
  ZSTD_customMem customMem;
  size_t staticSize;

  seqStore_t seqStore;  /* sequences storage ptrs */
  ldmState_t ldmState;  /* long distance matching state */
  rawSeq* ldmSequences; /* Storage for the ldm output sequences */
  size_t maxNbLdmSequences;
  rawSeqStore_t externSeqStore; /* Mutable reference to external sequences */
  ZSTD_blockState_t blockState;
  U32* entropyWorkspace; /* entropy workspace of HUF_WORKSPACE_SIZE bytes */

  /* streaming */
  char* inBuff;
  size_t inBuffSize;
  size_t inToCompress;
  size_t inBuffPos;
  size_t inBuffTarget;
  char* outBuff;
  size_t outBuffSize;
  size_t outBuffContentSize;
  size_t outBuffFlushedSize;
  ZSTD_cStreamStage streamStage;
  U32 frameEnded;

  /* Dictionary */
  ZSTD_CDict* cdictLocal;
  const ZSTD_CDict* cdict;
  ZSTD_prefixDict prefixDict; /* single-usage dictionary */

  /* Multi-threading */
#ifdef ZSTD_MULTITHREAD
  ZSTDMT_CCtx* mtctx;
#endif
};

typedef enum { ZSTD_dtlm_fast, ZSTD_dtlm_full } ZSTD_dictTableLoadMethod_e;

typedef enum { ZSTD_noDict = 0, ZSTD_extDict = 1, ZSTD_dictMatchState = 2 } ZSTD_dictMode_e;

typedef size_t (*ZSTD_blockCompressor)(
    ZSTD_matchState_t* bs, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM], void const* src, size_t srcSize);
ZSTD_blockCompressor ZSTD_selectBlockCompressor(ZSTD_strategy strat, ZSTD_dictMode_e dictMode);

MEM_STATIC U32 ZSTD_LLcode(U32 litLength)
{
  static const BYTE LL_Code[64] = {0,
      1,
      2,
      3,
      4,
      5,
      6,
      7,
      8,
      9,
      10,
      11,
      12,
      13,
      14,
      15,
      16,
      16,
      17,
      17,
      18,
      18,
      19,
      19,
      20,
      20,
      20,
      20,
      21,
      21,
      21,
      21,
      22,
      22,
      22,
      22,
      22,
      22,
      22,
      22,
      23,
      23,
      23,
      23,
      23,
      23,
      23,
      23,
      24,
      24,
      24,
      24,
      24,
      24,
      24,
      24,
      24,
      24,
      24,
      24,
      24,
      24,
      24,
      24};
  static const U32 LL_deltaCode = 19;
  return (litLength > 63) ? ZSTD_highbit32(litLength) + LL_deltaCode : LL_Code[litLength];
}

/* ZSTD_MLcode() :
 * note : mlBase = matchLength - MINMATCH;
 *        because it's the format it's stored in seqStore->sequences */
MEM_STATIC U32 ZSTD_MLcode(U32 mlBase)
{
  static const BYTE ML_Code[128] = {0,
      1,
      2,
      3,
      4,
      5,
      6,
      7,
      8,
      9,
      10,
      11,
      12,
      13,
      14,
      15,
      16,
      17,
      18,
      19,
      20,
      21,
      22,
      23,
      24,
      25,
      26,
      27,
      28,
      29,
      30,
      31,
      32,
      32,
      33,
      33,
      34,
      34,
      35,
      35,
      36,
      36,
      36,
      36,
      37,
      37,
      37,
      37,
      38,
      38,
      38,
      38,
      38,
      38,
      38,
      38,
      39,
      39,
      39,
      39,
      39,
      39,
      39,
      39,
      40,
      40,
      40,
      40,
      40,
      40,
      40,
      40,
      40,
      40,
      40,
      40,
      40,
      40,
      40,
      40,
      41,
      41,
      41,
      41,
      41,
      41,
      41,
      41,
      41,
      41,
      41,
      41,
      41,
      41,
      41,
      41,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42,
      42};
  static const U32 ML_deltaCode = 36;
  return (mlBase > 127) ? ZSTD_highbit32(mlBase) + ML_deltaCode : ML_Code[mlBase];
}

/*! ZSTD_storeSeq() :
 *  Store a sequence (literal length, literals, offset code and match length code) into seqStore_t.
 *  `offsetCode` : distance to match + 3 (values 1-3 are repCodes).
 *  `mlBase` : matchLength - MINMATCH
 */
MEM_STATIC void ZSTD_storeSeq(
    seqStore_t* seqStorePtr, size_t litLength, const void* literals, U32 offsetCode, size_t mlBase)
{
#if defined(DEBUGLEVEL) && (DEBUGLEVEL >= 6)
  static const BYTE* g_start = NULL;
  if (g_start == NULL)
    g_start = (const BYTE*)literals; /* note : index only works for compression within a single segment */
  {
    U32 const pos = (U32)((const BYTE*)literals - g_start);
    DEBUGLOG(6,
        "Cpos%7u :%3u literals, match%4u bytes at offCode%7u",
        pos,
        (U32)litLength,
        (U32)mlBase + MINMATCH,
        (U32)offsetCode);
  }
#endif
  assert((size_t)(seqStorePtr->sequences - seqStorePtr->sequencesStart) < seqStorePtr->maxNbSeq);
  /* copy Literals */
  assert(seqStorePtr->maxNbLit <= 128 KB);
  assert(seqStorePtr->lit + litLength <= seqStorePtr->litStart + seqStorePtr->maxNbLit);
  ZSTD_wildcopy(seqStorePtr->lit, literals, litLength);
  seqStorePtr->lit += litLength;

  /* literal Length */
  if (litLength > 0xFFFF) {
    assert(seqStorePtr->longLengthID == 0); /* there can only be a single long length */
    seqStorePtr->longLengthID = 1;
    seqStorePtr->longLengthPos = (U32)(seqStorePtr->sequences - seqStorePtr->sequencesStart);
  }
  seqStorePtr->sequences[0].litLength = (U16)litLength;

  /* match offset */
  seqStorePtr->sequences[0].offset = offsetCode + 1;

  /* match Length */
  if (mlBase > 0xFFFF) {
    assert(seqStorePtr->longLengthID == 0); /* there can only be a single long length */
    seqStorePtr->longLengthID = 2;
    seqStorePtr->longLengthPos = (U32)(seqStorePtr->sequences - seqStorePtr->sequencesStart);
  }
  seqStorePtr->sequences[0].matchLength = (U16)mlBase;

  seqStorePtr->sequences++;
}

/*-*************************************
 *  Match length counter
 ***************************************/
static unsigned ZSTD_NbCommonBytes(size_t val)
{
  if (MEM_isLittleEndian()) {
    if (MEM_64bits()) {
#if defined(_MSC_VER) && defined(_WIN64)
      unsigned long r = 0;
      _BitScanForward64(&r, (U64)val);
      return (unsigned)(r >> 3);
#elif defined(__GNUC__) && (__GNUC__ >= 4)
      return (__builtin_ctzll((U64)val) >> 3);
#else
      static const int DeBruijnBytePos[64] = {0,
          0,
          0,
          0,
          0,
          1,
          1,
          2,
          0,
          3,
          1,
          3,
          1,
          4,
          2,
          7,
          0,
          2,
          3,
          6,
          1,
          5,
          3,
          5,
          1,
          3,
          4,
          4,
          2,
          5,
          6,
          7,
          7,
          0,
          1,
          2,
          3,
          3,
          4,
          6,
          2,
          6,
          5,
          5,
          3,
          4,
          5,
          6,
          7,
          1,
          2,
          4,
          6,
          4,
          4,
          5,
          7,
          2,
          6,
          5,
          7,
          6,
          7,
          7};
      return DeBruijnBytePos[((U64)((val & -(long long)val) * 0x0218A392CDABBD3FULL)) >> 58];
#endif
    } else { /* 32 bits */
#if defined(_MSC_VER)
      unsigned long r = 0;
      _BitScanForward(&r, (U32)val);
      return (unsigned)(r >> 3);
#elif defined(__GNUC__) && (__GNUC__ >= 3)
      return (__builtin_ctz((U32)val) >> 3);
#else
      static const int DeBruijnBytePos[32] = {
          0, 0, 3, 0, 3, 1, 3, 0, 3, 2, 2, 1, 3, 2, 0, 1, 3, 3, 1, 2, 2, 2, 2, 0, 3, 1, 2, 0, 1, 0, 1, 1};
      return DeBruijnBytePos[((U32)((val & -(S32)val) * 0x077CB531U)) >> 27];
#endif
    }
  } else { /* Big Endian CPU */
    if (MEM_64bits()) {
#if defined(_MSC_VER) && defined(_WIN64)
      unsigned long r = 0;
      _BitScanReverse64(&r, val);
      return (unsigned)(r >> 3);
#elif defined(__GNUC__) && (__GNUC__ >= 4)
      return (__builtin_clzll(val) >> 3);
#else
      unsigned r;
      const unsigned n32 = sizeof(size_t) * 4; /* calculate this way due to compiler complaining in 32-bits mode */
      if (!(val >> n32)) {
        r = 4;
      } else {
        r = 0;
        val >>= n32;
      }
      if (!(val >> 16)) {
        r += 2;
        val >>= 8;
      } else {
        val >>= 24;
      }
      r += (!val);
      return r;
#endif
    } else { /* 32 bits */
#if defined(_MSC_VER)
      unsigned long r = 0;
      _BitScanReverse(&r, (unsigned long)val);
      return (unsigned)(r >> 3);
#elif defined(__GNUC__) && (__GNUC__ >= 3)
      return (__builtin_clz((U32)val) >> 3);
#else
      unsigned r;
      if (!(val >> 16)) {
        r = 2;
        val >>= 8;
      } else {
        r = 0;
        val >>= 24;
      }
      r += (!val);
      return r;
#endif
    }
  }
}

MEM_STATIC size_t ZSTD_count(const BYTE* pIn, const BYTE* pMatch, const BYTE* const pInLimit)
{
  const BYTE* const pStart = pIn;
  const BYTE* const pInLoopLimit = pInLimit - (sizeof(size_t) - 1);

  if (pIn < pInLoopLimit) {
    {
      size_t const diff = MEM_readST(pMatch) ^ MEM_readST(pIn);
      if (diff)
        return ZSTD_NbCommonBytes(diff);
    }
    pIn += sizeof(size_t);
    pMatch += sizeof(size_t);
    while (pIn < pInLoopLimit) {
      size_t const diff = MEM_readST(pMatch) ^ MEM_readST(pIn);
      if (!diff) {
        pIn += sizeof(size_t);
        pMatch += sizeof(size_t);
        continue;
      }
      pIn += ZSTD_NbCommonBytes(diff);
      return (size_t)(pIn - pStart);
    }
  }
  if (MEM_64bits() && (pIn < (pInLimit - 3)) && (MEM_read32(pMatch) == MEM_read32(pIn))) {
    pIn += 4;
    pMatch += 4;
  }
  if ((pIn < (pInLimit - 1)) && (MEM_read16(pMatch) == MEM_read16(pIn))) {
    pIn += 2;
    pMatch += 2;
  }
  if ((pIn < pInLimit) && (*pMatch == *pIn))
    pIn++;
  return (size_t)(pIn - pStart);
}

/** ZSTD_count_2segments() :
 *  can count match length with `ip` & `match` in 2 different segments.
 *  convention : on reaching mEnd, match count continue starting from iStart
 */
MEM_STATIC size_t ZSTD_count_2segments(
    const BYTE* ip, const BYTE* match, const BYTE* iEnd, const BYTE* mEnd, const BYTE* iStart)
{
  const BYTE* const vEnd = MIN(ip + (mEnd - match), iEnd);
  size_t const matchLength = ZSTD_count(ip, match, vEnd);
  if (match + matchLength != mEnd)
    return matchLength;
  DEBUGLOG(7, "ZSTD_count_2segments: found a 2-parts match (current length==%zu)", matchLength);
  DEBUGLOG(7, "distance from match beginning to end dictionary = %zi", mEnd - match);
  DEBUGLOG(7, "distance from current pos to end buffer = %zi", iEnd - ip);
  DEBUGLOG(7, "next byte : ip==%02X, istart==%02X", ip[matchLength], *iStart);
  DEBUGLOG(7, "final match length = %zu", matchLength + ZSTD_count(ip + matchLength, iStart, iEnd));
  return matchLength + ZSTD_count(ip + matchLength, iStart, iEnd);
}

/*-*************************************
 *  Hashes
 ***************************************/
static const U32 prime3bytes = 506832829U;
static U32 ZSTD_hash3(U32 u, U32 h)
{
  return ((u << (32 - 24)) * prime3bytes) >> (32 - h);
}
MEM_STATIC size_t ZSTD_hash3Ptr(const void* ptr, U32 h)
{
  return ZSTD_hash3(MEM_readLE32(ptr), h);
} /* only in zstd_opt.h */

static const U32 prime4bytes = 2654435761U;
static U32 ZSTD_hash4(U32 u, U32 h)
{
  return (u * prime4bytes) >> (32 - h);
}
static size_t ZSTD_hash4Ptr(const void* ptr, U32 h)
{
  return ZSTD_hash4(MEM_read32(ptr), h);
}

static const U64 prime5bytes = 889523592379ULL;
static size_t ZSTD_hash5(U64 u, U32 h)
{
  return (size_t)(((u << (64 - 40)) * prime5bytes) >> (64 - h));
}
static size_t ZSTD_hash5Ptr(const void* p, U32 h)
{
  return ZSTD_hash5(MEM_readLE64(p), h);
}

static const U64 prime6bytes = 227718039650203ULL;
static size_t ZSTD_hash6(U64 u, U32 h)
{
  return (size_t)(((u << (64 - 48)) * prime6bytes) >> (64 - h));
}
static size_t ZSTD_hash6Ptr(const void* p, U32 h)
{
  return ZSTD_hash6(MEM_readLE64(p), h);
}

static const U64 prime7bytes = 58295818150454627ULL;
static size_t ZSTD_hash7(U64 u, U32 h)
{
  return (size_t)(((u << (64 - 56)) * prime7bytes) >> (64 - h));
}
static size_t ZSTD_hash7Ptr(const void* p, U32 h)
{
  return ZSTD_hash7(MEM_readLE64(p), h);
}

static const U64 prime8bytes = 0xCF1BBCDCB7A56463ULL;
static size_t ZSTD_hash8(U64 u, U32 h)
{
  return (size_t)(((u)*prime8bytes) >> (64 - h));
}
static size_t ZSTD_hash8Ptr(const void* p, U32 h)
{
  return ZSTD_hash8(MEM_readLE64(p), h);
}

MEM_STATIC size_t ZSTD_hashPtr(const void* p, U32 hBits, U32 mls)
{
  switch (mls) {
    default:
    case 4:
      return ZSTD_hash4Ptr(p, hBits);
    case 5:
      return ZSTD_hash5Ptr(p, hBits);
    case 6:
      return ZSTD_hash6Ptr(p, hBits);
    case 7:
      return ZSTD_hash7Ptr(p, hBits);
    case 8:
      return ZSTD_hash8Ptr(p, hBits);
  }
}

/** ZSTD_ipow() :
 * Return base^exponent.
 */
static U64 ZSTD_ipow(U64 base, U64 exponent)
{
  U64 power = 1;
  while (exponent) {
    if (exponent & 1)
      power *= base;
    exponent >>= 1;
    base *= base;
  }
  return power;
}

#define ZSTD_ROLL_HASH_CHAR_OFFSET 10

/** ZSTD_rollingHash_append() :
 * Add the buffer to the hash value.
 */
static U64 ZSTD_rollingHash_append(U64 hash, void const* buf, size_t size)
{
  BYTE const* istart = (BYTE const*)buf;
  size_t pos;
  for (pos = 0; pos < size; ++pos) {
    hash *= prime8bytes;
    hash += istart[pos] + ZSTD_ROLL_HASH_CHAR_OFFSET;
  }
  return hash;
}

/** ZSTD_rollingHash_compute() :
 * Compute the rolling hash value of the buffer.
 */
MEM_STATIC U64 ZSTD_rollingHash_compute(void const* buf, size_t size)
{
  return ZSTD_rollingHash_append(0, buf, size);
}

/** ZSTD_rollingHash_primePower() :
 * Compute the primePower to be passed to ZSTD_rollingHash_rotate() for a hash
 * over a window of length bytes.
 */
MEM_STATIC U64 ZSTD_rollingHash_primePower(U32 length)
{
  return ZSTD_ipow(prime8bytes, length - 1);
}

/** ZSTD_rollingHash_rotate() :
 * Rotate the rolling hash by one byte.
 */
MEM_STATIC U64 ZSTD_rollingHash_rotate(U64 hash, BYTE toRemove, BYTE toAdd, U64 primePower)
{
  hash -= (toRemove + ZSTD_ROLL_HASH_CHAR_OFFSET) * primePower;
  hash *= prime8bytes;
  hash += toAdd + ZSTD_ROLL_HASH_CHAR_OFFSET;
  return hash;
}

/*-*************************************
 *  Round buffer management
 ***************************************/
/* Max current allowed */
#define ZSTD_CURRENT_MAX ((3U << 29) + (1U << ZSTD_WINDOWLOG_MAX))
/* Maximum chunk size before overflow correction needs to be called again */
#define ZSTD_CHUNKSIZE_MAX                                   \
  (((U32)-1)              /* Maximum ending current index */ \
      - ZSTD_CURRENT_MAX) /* Maximum beginning lowLimit */

/**
 * ZSTD_window_clear():
 * Clears the window containing the history by simply setting it to empty.
 */
MEM_STATIC void ZSTD_window_clear(ZSTD_window_t* window)
{
  size_t const endT = (size_t)(window->nextSrc - window->base);
  U32 const end = (U32)endT;

  window->lowLimit = end;
  window->dictLimit = end;
}

/**
 * ZSTD_window_hasExtDict():
 * Returns non-zero if the window has a non-empty extDict.
 */
MEM_STATIC U32 ZSTD_window_hasExtDict(ZSTD_window_t const window)
{
  return window.lowLimit < window.dictLimit;
}

/**
 * ZSTD_matchState_dictMode():
 * Inspects the provided matchState and figures out what dictMode should be
 * passed to the compressor.
 */
MEM_STATIC ZSTD_dictMode_e ZSTD_matchState_dictMode(const ZSTD_matchState_t* ms)
{
  return ZSTD_window_hasExtDict(ms->window) ? ZSTD_extDict
         : ms->dictMatchState != NULL       ? ZSTD_dictMatchState
                                            : ZSTD_noDict;
}

/**
 * ZSTD_window_needOverflowCorrection():
 * Returns non-zero if the indices are getting too large and need overflow
 * protection.
 */
MEM_STATIC U32 ZSTD_window_needOverflowCorrection(ZSTD_window_t const window, void const* srcEnd)
{
  U32 const current = (U32)((BYTE const*)srcEnd - window.base);
  return current > ZSTD_CURRENT_MAX;
}

/**
 * ZSTD_window_correctOverflow():
 * Reduces the indices to protect from index overflow.
 * Returns the correction made to the indices, which must be applied to every
 * stored index.
 *
 * The least significant cycleLog bits of the indices must remain the same,
 * which may be 0. Every index up to maxDist in the past must be valid.
 * NOTE: (maxDist & cycleMask) must be zero.
 */
MEM_STATIC U32 ZSTD_window_correctOverflow(ZSTD_window_t* window, U32 cycleLog, U32 maxDist, void const* src)
{
  /* preemptive overflow correction:
   * 1. correction is large enough:
   *    lowLimit > (3<<29) ==> current > 3<<29 + 1<<windowLog
   *    1<<windowLog <= newCurrent < 1<<chainLog + 1<<windowLog
   *
   *    current - newCurrent
   *    > (3<<29 + 1<<windowLog) - (1<<windowLog + 1<<chainLog)
   *    > (3<<29) - (1<<chainLog)
   *    > (3<<29) - (1<<30)             (NOTE: chainLog <= 30)
   *    > 1<<29
   *
   * 2. (ip+ZSTD_CHUNKSIZE_MAX - cctx->base) doesn't overflow:
   *    After correction, current is less than (1<<chainLog + 1<<windowLog).
   *    In 64-bit mode we are safe, because we have 64-bit ptrdiff_t.
   *    In 32-bit mode we are safe, because (chainLog <= 29), so
   *    ip+ZSTD_CHUNKSIZE_MAX - cctx->base < 1<<32.
   * 3. (cctx->lowLimit + 1<<windowLog) < 1<<32:
   *    windowLog <= 31 ==> 3<<29 + 1<<windowLog < 7<<29 < 1<<32.
   */
  U32 const cycleMask = (1U << cycleLog) - 1;
  U32 const current = (U32)((BYTE const*)src - window->base);
  U32 const newCurrent = (current & cycleMask) + maxDist;
  U32 const correction = current - newCurrent;
  assert((maxDist & cycleMask) == 0);
  assert(current > newCurrent);
  /* Loose bound, should be around 1<<29 (see above) */
  assert(correction > 1 << 28);

  window->base += correction;
  window->dictBase += correction;
  window->lowLimit -= correction;
  window->dictLimit -= correction;

  DEBUGLOG(4, "Correction of 0x%x bytes to lowLimit=0x%x", correction, window->lowLimit);
  return correction;
}

/**
 * ZSTD_window_enforceMaxDist():
 * Updates lowLimit so that:
 *    (srcEnd - base) - lowLimit == maxDist + loadedDictEnd
 *
 * This allows a simple check that index >= lowLimit to see if index is valid.
 * This must be called before a block compression call, with srcEnd as the block
 * source end.
 *
 * If loadedDictEndPtr is not NULL, we set it to zero once we update lowLimit.
 * This is because dictionaries are allowed to be referenced as long as the last
 * byte of the dictionary is in the window, but once they are out of range,
 * they cannot be referenced. If loadedDictEndPtr is NULL, we use
 * loadedDictEnd == 0.
 *
 * In normal dict mode, the dict is between lowLimit and dictLimit. In
 * dictMatchState mode, lowLimit and dictLimit are the same, and the dictionary
 * is below them. forceWindow and dictMatchState are therefore incompatible.
 */
MEM_STATIC void ZSTD_window_enforceMaxDist(ZSTD_window_t* window, void const* srcEnd, U32 maxDist,
    U32* loadedDictEndPtr, const ZSTD_matchState_t** dictMatchStatePtr)
{
  U32 const blockEndIdx = (U32)((BYTE const*)srcEnd - window->base);
  U32 loadedDictEnd = (loadedDictEndPtr != NULL) ? *loadedDictEndPtr : 0;
  DEBUGLOG(5, "ZSTD_window_enforceMaxDist: blockEndIdx=%u, maxDist=%u", (unsigned)blockEndIdx, (unsigned)maxDist);
  if (blockEndIdx > maxDist + loadedDictEnd) {
    U32 const newLowLimit = blockEndIdx - maxDist;
    if (window->lowLimit < newLowLimit)
      window->lowLimit = newLowLimit;
    if (window->dictLimit < window->lowLimit) {
      DEBUGLOG(5,
          "Update dictLimit to match lowLimit, from %u to %u",
          (unsigned)window->dictLimit,
          (unsigned)window->lowLimit);
      window->dictLimit = window->lowLimit;
    }
    if (loadedDictEndPtr)
      *loadedDictEndPtr = 0;
    if (dictMatchStatePtr)
      *dictMatchStatePtr = NULL;
  }
}

/**
 * ZSTD_window_update():
 * Updates the window by appending [src, src + srcSize) to the window.
 * If it is not contiguous, the current prefix becomes the extDict, and we
 * forget about the extDict. Handles overlap of the prefix and extDict.
 * Returns non-zero if the segment is contiguous.
 */
MEM_STATIC U32 ZSTD_window_update(ZSTD_window_t* window, void const* src, size_t srcSize)
{
  BYTE const* const ip = (BYTE const*)src;
  U32 contiguous = 1;
  DEBUGLOG(5, "ZSTD_window_update");
  /* Check if blocks follow each other */
  if (src != window->nextSrc) {
    /* not contiguous */
    size_t const distanceFromBase = (size_t)(window->nextSrc - window->base);
    DEBUGLOG(5, "Non contiguous blocks, new segment starts at %u", window->dictLimit);
    window->lowLimit = window->dictLimit;
    assert(distanceFromBase == (size_t)(U32)distanceFromBase); /* should never overflow */
    window->dictLimit = (U32)distanceFromBase;
    window->dictBase = window->base;
    window->base = ip - distanceFromBase;
    // ms->nextToUpdate = window->dictLimit;
    if (window->dictLimit - window->lowLimit < HASH_READ_SIZE)
      window->lowLimit = window->dictLimit; /* too small extDict */
    contiguous = 0;
  }
  window->nextSrc = ip + srcSize;
  /* if input and dictionary overlap : reduce dictionary (area presumed modified by input) */
  if ((ip + srcSize > window->dictBase + window->lowLimit) & (ip < window->dictBase + window->dictLimit)) {
    ptrdiff_t const highInputIdx = (ip + srcSize) - window->dictBase;
    U32 const lowLimitMax = (highInputIdx > (ptrdiff_t)window->dictLimit) ? window->dictLimit : (U32)highInputIdx;
    window->lowLimit = lowLimitMax;
    DEBUGLOG(5, "Overlapping extDict and input : new lowLimit = %u", window->lowLimit);
  }
  return contiguous;
}

/* debug functions */
#if (DEBUGLEVEL >= 2)

MEM_STATIC double ZSTD_fWeight(U32 rawStat)
{
  U32 const fp_accuracy = 8;
  U32 const fp_multiplier = (1 << fp_accuracy);
  U32 const newStat = rawStat + 1;
  U32 const hb = ZSTD_highbit32(newStat);
  U32 const BWeight = hb * fp_multiplier;
  U32 const FWeight = (newStat << fp_accuracy) >> hb;
  U32 const weight = BWeight + FWeight;
  assert(hb + fp_accuracy < 31);
  return (double)weight / fp_multiplier;
}

/* display a table content,
 * listing each element, its frequency, and its predicted bit cost */
MEM_STATIC void ZSTD_debugTable(const U32* table, U32 max)
{
  unsigned u, sum;
  for (u = 0, sum = 0; u <= max; u++)
    sum += table[u];
  DEBUGLOG(2, "total nb elts: %u", sum);
  for (u = 0; u <= max; u++) {
    DEBUGLOG(2, "%2u: %5u  (%.2f)", u, table[u], ZSTD_fWeight(sum) - ZSTD_fWeight(table[u]));
  }
}

#endif

#if defined(__cplusplus)
}
#endif

/* ==============================================================
 * Private declarations
 * These prototypes shall only be called from within lib/compress
 * ============================================================== */

/* ZSTD_getCParamsFromCCtxParams() :
 * cParams are built depending on compressionLevel, src size hints,
 * LDM and manually set compression parameters.
 */
ZSTD_compressionParameters ZSTD_getCParamsFromCCtxParams(
    const ZSTD_CCtx_params* CCtxParams, U64 srcSizeHint, size_t dictSize);

/*! ZSTD_initCStream_internal() :
 *  Private use only. Init streaming operation.
 *  expects params to be valid.
 *  must receive dict, or cdict, or none, but not both.
 *  @return : 0, or an error code */
size_t ZSTD_initCStream_internal(ZSTD_CStream* zcs, const void* dict, size_t dictSize, const ZSTD_CDict* cdict,
    ZSTD_CCtx_params params, unsigned long long pledgedSrcSize);

void ZSTD_resetSeqStore(seqStore_t* ssPtr);

/*! ZSTD_compressStream_generic() :
 *  Private use only. To be called from zstdmt_compress.c in single-thread mode. */
size_t ZSTD_compressStream_generic(
    ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input, ZSTD_EndDirective const flushMode);

/*! ZSTD_getCParamsFromCDict() :
 *  as the name implies */
ZSTD_compressionParameters ZSTD_getCParamsFromCDict(const ZSTD_CDict* cdict);

/* ZSTD_compressBegin_advanced_internal() :
 * Private use only. To be called from zstdmt_compress.c. */
size_t ZSTD_compressBegin_advanced_internal(ZSTD_CCtx* cctx, const void* dict, size_t dictSize,
    ZSTD_dictContentType_e dictContentType, ZSTD_dictTableLoadMethod_e dtlm, const ZSTD_CDict* cdict,
    ZSTD_CCtx_params params, unsigned long long pledgedSrcSize);

/* ZSTD_compress_advanced_internal() :
 * Private use only. To be called from zstdmt_compress.c. */
size_t ZSTD_compress_advanced_internal(ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize,
    const void* dict, size_t dictSize, ZSTD_CCtx_params params);

/* ZSTD_writeLastEmptyBlock() :
 * output an empty Block with end-of-frame mark to complete a frame
 * @return : size of data written into `dst` (== ZSTD_blockHeaderSize (defined in zstd_internal.h))
 *           or an error code if `dstCapcity` is too small (<ZSTD_blockHeaderSize)
 */
size_t ZSTD_writeLastEmptyBlock(void* dst, size_t dstCapacity);

/* ZSTD_referenceExternalSequences() :
 * Must be called before starting a compression operation.
 * seqs must parse a prefix of the source.
 * This cannot be used when long range matching is enabled.
 * Zstd will use these sequences, and pass the literals to a secondary block
 * compressor.
 * @return : An error code on failure.
 * NOTE: seqs are not verified! Invalid sequences can cause out-of-bounds memory
 * access and data corruption.
 */
size_t ZSTD_referenceExternalSequences(ZSTD_CCtx* cctx, rawSeq* seq, size_t nbSeq);

#endif /* ZSTD_COMPRESS_H */
